U.S. patent number 9,156,861 [Application Number 14/241,581] was granted by the patent office on 2015-10-13 for method for preparing trialkoxysilane.
This patent grant is currently assigned to INSTITUTION OF ION-PLASMA AND LASER TECHNOLOGIES, OCI COMPANY LTD.. The grantee listed for this patent is Salimboev Akmal, Abdurakhmanov Boris, Ashurov Khatam, Ashurova Khekayat, Deok Yun Kim, Kyung Yeol Kim, Yong Il Kim, Saidov Sabir, Salikhov Shavkat, Azizov Sultan, Rotshteyn Vladimir, Se In Yang. Invention is credited to Salimboev Akmal, Abdurakhmanov Boris, Ashurov Khatam, Ashurova Khekayat, Deok Yun Kim, Kyung Yeol Kim, Yong Il Kim, Saidov Sabir, Salikhov Shavkat, Azizov Sultan, Rotshteyn Vladimir, Se In Yang.
United States Patent |
9,156,861 |
Yang , et al. |
October 13, 2015 |
Method for preparing trialkoxysilane
Abstract
The present invention relates to a method for preparing
SiH(OR.sub.3)-type trialkoxysilane (wherein, R is a C1-C3 methyl,
ethyl, propyl or isopropyl group), and more specifically, the
method comprises the steps of: preventing the oxidation of a
silicon surface by pulverizing raw silicon material in a solvent
environment without contact with the air so that the initial
induction period of the direct synthesis of trialkoxysilane is
dramatically reduced; and removing impurities from a reaction
environment by continuously selecting a part of the solvent through
a membrane filter provided in a reactor body.
Inventors: |
Yang; Se In (Seongnam-si,
KR), Kim; Yong Il (Incheon, KR), Kim; Kyung
Yeol (Seoul, KR), Kim; Deok Yun (Seongnam-si,
KR), Khatam; Ashurov (Tashkent, UZ), Boris;
Abdurakhmanov (Tashkent, UZ), Vladimir; Rotshteyn
(Tashkent, UZ), Shavkat; Salikhov (Tashkent,
UZ), Khekayat; Ashurova (Tashkent, UZ),
Akmal; Salimboev (Tashkent viloyat, UZ), Sultan;
Azizov (Tashkent, UZ), Sabir; Saidov (Tashkent,
UZ) |
Applicant: |
Name |
City |
State |
Country |
Type |
Yang; Se In
Kim; Yong Il
Kim; Kyung Yeol
Kim; Deok Yun
Khatam; Ashurov
Boris; Abdurakhmanov
Vladimir; Rotshteyn
Shavkat; Salikhov
Khekayat; Ashurova
Akmal; Salimboev
Sultan; Azizov
Sabir; Saidov |
Seongnam-si
Incheon
Seoul
Seongnam-si
Tashkent
Tashkent
Tashkent
Tashkent
Tashkent
Tashkent viloyat
Tashkent
Tashkent |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
KR
KR
KR
KR
UZ
UZ
UZ
UZ
UZ
UZ
UZ
UZ |
|
|
Assignee: |
OCI COMPANY LTD. (Seoul,
KR)
INSTITUTION OF ION-PLASMA AND LASER TECHNOLOGIES (Tashkent,
UZ)
|
Family
ID: |
47832369 |
Appl.
No.: |
14/241,581 |
Filed: |
March 30, 2012 |
PCT
Filed: |
March 30, 2012 |
PCT No.: |
PCT/KR2012/002428 |
371(c)(1),(2),(4) Date: |
February 27, 2014 |
PCT
Pub. No.: |
WO2013/035956 |
PCT
Pub. Date: |
March 14, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140364639 A1 |
Dec 11, 2014 |
|
Foreign Application Priority Data
|
|
|
|
|
Sep 6, 2011 [UZ] |
|
|
20110393 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J
23/72 (20130101); C07F 7/025 (20130101); C07F
7/04 (20130101) |
Current International
Class: |
C07F
7/00 (20060101); C07F 7/02 (20060101); B01J
23/72 (20060101); C07F 7/04 (20060101) |
Field of
Search: |
;556/472 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
0517398 |
|
Dec 1992 |
|
EP |
|
2263113 |
|
Jul 1993 |
|
GB |
|
S5034540 |
|
Nov 1975 |
|
JP |
|
S511692 |
|
Jan 1976 |
|
JP |
|
05178864 |
|
Jul 1993 |
|
JP |
|
06065258 |
|
Mar 1994 |
|
JP |
|
06312992 |
|
Nov 1994 |
|
JP |
|
06312994 |
|
Nov 1994 |
|
JP |
|
1020030077594 |
|
Oct 2003 |
|
KR |
|
100625148 |
|
Sep 2006 |
|
KR |
|
2235726 |
|
Sep 2004 |
|
RU |
|
2007032865 |
|
Mar 2007 |
|
WO |
|
Other References
International Search Report for PCT/KR2012/002428 mailed on Oct.
18, 2012. cited by applicant.
|
Primary Examiner: Gonzalez; Porfirio Nazario
Attorney, Agent or Firm: Lowe Hauptman & Ham, LLP
Claims
The invention claimed is:
1. A method for preparing trialkoxysilane comprising: (a)
pulverizing silicon (Si) into fine particles having a size of
30-100 .mu.m in a solvent environment, wherein the solvent is
directly used in a later synthesis of alkoxysilane; (b)
continuously synthesizing trialkoxysilane by continuously feeding a
suspension of silicon and anhydrous alcohol in an amount consumed
in a reaction in a synthesis process of trialkoxysilane to a
reactor, wherein the amount of consumed suspension is calculated
from an amount of synthesized trialkoxysilane using following
Equation 1, so that an amount of silicon fed to a reactor as a
suspension component, and an amount of silicon after a reaction is
completed in a reaction process are maintained the same, thereby
feeding a suspension so that a reaction proceeds consistently and
stably, mSi=k1mTES+k2mTEOS [Equation 1] wherein, mSi is mass of
silicon to feed to a reactor as a suspension component mTES is mass
of triethoxysilane obtained per unit time, mTEOS is mass of
tetraethoxysilane obtained per unit time, k1 is atomic weight of
Si/molar mass of TES obtained per unit time, and k2 is atomic
weight of Si/molar mass of TEOS obtained per unit time; and (c)
removing impurities accumulated by continuously bleeding a solvent
using a ceramic membrane filter.
2. The method of claim 1, wherein the silicon has a linear
dimension of 20 mm to 20 cm prior to pulverizing.
3. The method of claim 1, wherein a mass ratio of the solvent and
the silicon is 1:2 to 2:1.
4. The method of claim 1, wherein the catalyst is directly put into
a silicon mass in an amount of 1.0 to 10.0 wt % in the pulverizing
process in a solvent environment.
5. The method of claim 4, wherein the catalyst is a
copper-containing catalyst.
6. The method of claim 1, wherein the solvent is heated to 160 to
300.degree. C. in the synthesis process of trialkoxysilane.
7. The method of claim 1, wherein in the pulverizing of silicon, a
copper-containing catalyst is used, anhydrous methanol or anhydrous
ethanol is used as the anhydrous alcohol, and in the synthesis of
trialkoxysilane, the solvent is heated to 160 to 300.degree. C.,
while steps (a), (b) and (c) subsequently proceed.
8. The method of claim 1, wherein the suspension is continuously
mixed before fed to a reactor, in order to maintain a stable ratio
of silicon, solvent, and catalyst.
9. The method of claim 1, wherein the solvent is bled through a
ceramic membrane filter equipped in a reactor body in a reaction
process with impurities dissolved in the solvent.
10. The method of claim 1, wherein the ceramic membrane has a pore
size of 1 to 10 .mu.m.
11. The method of claim 1, wherein the amounts of the silicon, the
solvent, and the catalyst in a reaction environment are constantly
maintained throughout the entire synthesis processes of
trialkoxysilane.
12. The method of claim 1, wherein the trialkoxysilane is
represented by following Chemical Formula 1: SiH(OR).sub.3
[Chemical Formula 1] wherein, R is methyl, ethyl, propyl or
isopropyl group having 1 to 3 carbon atoms.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of Uzbekistan Patent
Application No. IAP 20110393 filed on Sep. 6, 2011 in the Korean
Patent and Trademark Office. Further, this application is the
National Phase application of International Application No.
PCT/KR2012/002428 filed on Mar. 30, 2012, which is incorporated
herein by reference in its entirety.
TECHNICAL FIELD
The present invention relates to a method for preparing
trialkoxysilane, and more particularly, to a method for preparing
SiH(OR).sub.3-type trialkoxysilane (wherein, R is methyl, ethyl,
propyl or isopropyl group having 1 to 3 carbon atoms).
BACKGROUND ART
Herein, the number in parenthesis [ ] refers to the number of
related art document cited for reference.
Trialkoxysilane is used in various fields such as production of
siliceous oligomer, monosilane, silicon for solar energy or
semiconductor, and the like, and for synthesis of such
trialkoxysilane, two basic methods are used.
First method is to synthesize trialkoxysilane in fixed bed or
fluidized bed under a vapor-gas environment. The method for
preparation in a vapor-gas environment is to pass alcohol vapor
through a silicon powder layer including catalyst in fixed bed or
fluidized bed. However, a fixed bed reactor is not widely-used
because of the difficulty of maintenance of uniformly distributed
temperature throughout the whole reactor volume. In case of direct
synthesis in fluidized bed, such disadvantage is avoidable.
In [1], a method for diluting gas in alcohol vapor may be used to
prevent or minimize that temperature in fluidized bed reaches peak.
As a diluting gas, argon, nitrogen, helium, neon, hydrogen, and the
like may be used. However, if additional material is applied,
production cost, and also losses of trialkoxysilane and alcohol
caused by the carryover of inert gas are increased. Meanwhile, the
output power of desired trialkoxysilane is improved by synthesis
under a lower pressure. In this case, conversion rate of silicon is
90%, selectivity of silicon is 84.2%, while under a normal
pressure, 65%, and 48.8%, respectively. However, there is a
disadvantage in that as pressure is lowered, reaction rate
decreases, and as a result, productivity is deteriorated.
[2] suggests passing hydrogen with alcohol vapor through contact
mass. If hydrogen is applied to the technical process of
preparation of trialkoxysilane, additional preparing and purifying
parts for hydrogen are needed, which increases preparation cost.
When contact mass was activated with nitrogen, and zinc was added
as an accelerator at reaction temperature of 280.degree. C. or
less, the content of triethoxysilane in reacting materials was 87%,
but the conversion rate of silicon was very low, 23%.
It is preferred to stepwise carry out the activation of contact
mass including silicon and a catalyst, at 450.degree. C. or less in
[1], or at 300-350.degree. C. in [2] and [5], under a nitrogen or
other inert gas atmosphere.
[6] to [9] suggest a method of applying hydrogen for silicon and
catalyst activation. Activation using hydrogen is carried out at
about 400.degree. C. in fixed bed or fluidized bed. The mixture of
silicon and catalyst contains 1.5% or more of copper. However, any
information as to the resulting selectivity, reactivity, and
reaction stability is not presented.
In [1] to [9], as a result of synthesis in fluidized bed for
obtaining triethoxysilane, in case the reaction is carried out
under atmospheric pressure, the yield of triethoxysilane and the
conversion rate of silicon are not high, and in case the reaction
is carried out under low pressure, main synthesis index is
improved, but such advantage is offset by consequent technical
features. In addition, in case liquefied material is additionally
injected with alcohol, some numerical values increase, but some
problems arise in the synthesis process of trialkoxysilane in
fluidized bed, and minor carryover of silicon and catalyst
necessarily occurs, thereby requiring an additional filtering
process for final product.
Second method is to carry out a direct reaction between silicon and
alcohol in suspension state in the liquid solvent environment of a
reactor equipped with a stirring device. This method is recently
widely used, because in case of using a solvent, the temperature of
reaction mixture may be uniformly maintained to greatly reduce the
possibility of overheating reaction environment, and prevent side
reaction, thereby raising the selectivity of trialkoxysilane and
the conversion rate of silicon.
In the synthesis of trialkoxysilane, the temperature is maintained
high, up to 300.degree. C., and thus, a solvent used in the
synthesis should not be decomposed at such temperature. Solvent
should effectively maintain uniform temperature in reaction system.
In addition, it should not generate oxidation at reaction
temperature ranging 100-300.degree. C., as well as highly disperse
the powder.
[10] and [11] suggest using alkylated benzene, and [12] suggests
using alkylated naphthalene-"THERMINOL" oil. Details of high
temperature solvents of THERMINOL.RTM. 59, 60, 66, DOWTHERM.RTM.
HT, MARLOTHERM.RTM. S, MARLOTHERM.RTM. and other trademarks are
described in [13] and [25].
[13], [14] and [15] suggest that the amount of solvent used in
synthesis should be 1:2-4:1 of solvent:silicon, preferably
1:1-2:1.
In [16]-[20], it takes a considerable induction period to activate
the reaction after pouring reaction raw materials of silicon and
alcohol, which may last for 1 hour to 12 hours. The main reason for
generation of induction period is an oxide film on the surface of
silicon. In order to reduce induction period, it is suggested that
activation step should be added in the synthesis process of
trialkoxysilane.
[13] reviews the activation process in very detail. Activation may
be carried out in the corresponding reactor in which the reaction
proceeds or a separate equipment. It is preferred to move silicon
activated in a separate equipment from dry neutral environment to
the reactor. Activation is carried out at 20 to 400.degree. C.,
preferably 150 to 300.degree. C. It is suggested that hydrogen and
nitrogen are used together as activating gas, and silicon is
activated by methanol for the reaction with ethanol, because
methanol has higher reaction activity to silicon than ethanol or
higher alcohol. For example, if 5% of methanol is added to ethanol,
reaction rate significantly increases. Herein, a reaction
suspension containing 1 kg of silicon, 14.1 g of copper hydroxide,
and 2.1 kg of solvent Marlotherm.RTM.S was activated at 150 to
250.degree. C. for 65 minutes using hydrogen and nitrogen. Methanol
was fed at 250.degree. C. for 5 hours at a rate of 4.3 g/min.
Thereafter, the temperature was lowered to 230.degree. C., the feed
of methanol was stopped, and ethanol was fed at the same rate,
wherein the feed of hydrogen was stopped, and that of nitrogen was
sustained. The total amount of activating material is
stoichiometrically calculated, and enough to convert divalent or
monovalent copper catalyst to free copper. It takes considerable
time for an actual activity process, and it is asserted that it is
caused by a large silicon-copper mass surface (fine particle
diameter of silicon 50-300 .mu.m). Meanwhile, a special condition
as to granularity of used catalyst is required. Fine particle size
should range 1-100 .mu.m, preferably 0.1-50 .mu.m, more preferably
0.1-30 .mu.m. At the same time, specific surface area of the
catalyst within a raw material is 0.1-2 m.sup.2/g, preferably 10-50
m.sup.2/g. Direct synthesis reaction of silicon using alcohol is
feasible both in periodic mode and continuous mode. In periodic
mode, all silicon is put into a reactor early in the process, while
alcohol is continuously fed until all silicon is reacted. Depending
on the output, it is also possible that a certain amount of silicon
is fed in turn, and alcohol is continuously fed. In case of a
reactor in continuous mode, only silicon or silicon containing a
catalyst is added after starting process. In this case, the content
of catalyst is minimum, or controlled so that side reaction
decomposing alcohol does not occur. Reaction temperature is
150.degree. C. or more, but not higher than the temperature where
the decomposition of alcohol and solvent occurs. It is preferred to
carry out the reaction at 200-260.degree. C. In methanol reaction,
220-250.degree. C. is preferred, and in ethanol reaction,
200-240.degree. C. is preferred. It is possible to carry out the
direct synthesis reaction of trialkoxysilane at both high pressure
and low pressure, but atmospheric pressure is preferred.
[21] and [22] suggest treating powdered silicon with hydrogen
fluoride in order to remove an oxide film on silicon surface prior
to working for shortening induction period.
[10] and [22] suggest activating reaction mass by maintaining high
temperature under a nitrogen, argon, and other inert environment,
and [23] suggests pre-mixing silicon and a catalyst in mill for 8
hours in an inert atmospheric condition, respectively.
[21] suggests injecting alkyl chloride, hydrogen chloride, or
ammonium chloride for activating silicon prior to synthesis, and
[24] suggests injecting halides such as NH.sub.4HF.sub.2. However,
in case materials such as halide, alkyl halide and methanol are
injected to a reactor prior to synthesis, a distillation step of
aimed material is added for removing impurities in aimed material,
which means that the preparation technique of trialkoxysilane
becomes complicated.
Therefore, it is appreciated that induction period in a direct
synthesis process of trialkoxysilane is not simply understood, and
effective solution therefor does not exist. In case of injecting an
additional reagent in synthesis process, the reagent should be
removed from the final product, which adds a further step, and
consequently makes the preparation technique of trialkoxysilane
complicated and its production cost high.
In [11], [13], [14], [17] and [21], the main synthesis reaction of
trialkoxysilane is accompanied by a side reaction which may form
oligoalkoxysiloxane, moisture and other side reaction products, and
they may be gradually accumulated under reaction environment to
lower reaction rate of synthesis process. In [14], the reason is
that metal being in the form of impurity in the synthesis of
silicon may be contained in a catalyst and used. Copper metal is
accumulated in a solvent component as a result of decomposition of
a catalyst. If silicon and trialkoxysilane containing such
remaining silicon and impurities are accumulated, reaction rate
decreases. In such case, in order to continuously use a solvent in
synthesis process of trialkoxysilane, the solvent must be
regenerated.
[16] suggests using aluminium (0.01-10%, preferably 0.1-2%), [2]
suggests using zinc, [25] suggests using an organic or inorganic
compound possessing at least one phosphorus-oxygen bond, as an
accelerators of reaction forming trialkoxysilane for increasing
efficiency of main synthesis index of trialkoxysilane. However, any
information about the effects therefrom is not provided.
[1] suggests a process for producing trialkoxysilane comprising
pulverizing silicon and performing interaction of ground silicon
and alcohol under the action of a catalyst.
Industrial silicon ground to a particle size of 500 .mu.m in the
air is used as a feedstock. Ethanol and methanol are used as
alcohol reagents, and a copper-containing compound such as copper
(I) chloride (CuCl) is used as a catalyst. They are mixed with
ground silicon, and heated at 300.degree. C. or less for several
hours, thereby activating the catalyst to activate technical
interaction of alcohol and silicon. Such technical method is also
used in other methods similar to that of [1]. Together with this,
for the purpose of interaction of silicon and alcohol, an
additional catalyst in the form of halides is applied, and as
organic and inorganic materials containing a halogen component,
chlorides, fluorides, methyl bromide, ethyl bromide, ethylene
trichloride, hydrogen fluoride (HF), hydrogen chloride (HCl),
hydrogen bromide (HBr), hydrogen iodide (HI), and the like are
mentioned. The above method has significant disadvantages in spite
of its usability. The most important thing among those is
additional considerable energy loss caused by pre-heating treatment
at 300.degree. C. or less for a long period, thereby extending
entire processing time, and increasing energy consumption. In
addition, the technical measures to apply gas-type halides for
activation of process is not environmentally safe.
[26] includes pulverizing process of silicon, and interaction
process of alcohol and ground silicon through a catalyst in a
heated solvent environment with a reagent activated. Silicon is
milled to fine particles to a size of 500 .mu.m in the air using a
ball mill. As an alcohol reagent, ethanol and methanol are used,
and triethoxysilane and trimethoxysilane are obtained as a final
product. As a catalyst, usually a copper-containing compound,
mainly CuCl is used. As a solvent, polyaromatic oil is used, and
the main technical process of an interaction between milled silicon
and alcohol is performed under the environment where the solvent is
heated to 200.degree. C. The activation technique for an reagent is
applied, and the reason for applying such technique is as follows:
In the preparation of trialkoxysilane according to the illustrated
schematic, impurities in raw materials are accumulated in reaction
mass to make the consumption of reaction mass uneven, and solvent
is partly consumed in a side reaction caused by impurities in raw
materials, thereby generating unreacted silicon. Therefore, a
technique to activate reagent is applied, which bleeds and
participates a reaction mixture suspension containing unreacted
silicon, and adds an adequate amount of solvent and catalyst, to
return the concentrated suspension to the process. Such process is
carried out several times during technical processing as unreacted
silicon is accumulated in a reactor in the form of deposits. Like
other similar methods, in spite of decrease in side reaction,
increase in product yield, decrease in raw material loss, and
increase in equipment productivity, the method has a technical
disadvantage of having very complicated process, because the
process is activated by applied technical measures, that is,
separating unreacted silicon, and periodically repeated adding
concentrated mixture of solvent and catalyst to reaction mass, in
order to supplement the loss of solvent and catalyst. Moreover,
since it is possible to rapidly reduce or slow down the reaction in
the addition of an amount of new reagent instead of bled part, any
measures followed by remove or shortening of reaction induction
period are not considered.
RELATED ART DOCUMENT
Patent Document
[1] U.S. Pat. No. 5,260,471: Process for producing
trialkoxysilane/Yashinori Yamada 1993. [2] U.S. Pat. No. 3,072,700:
Process for producing silanes/Nicolas P. V. de with 1963. [3]
Japanese Patent Laid-Open Publication No. 06-065258: Preparation of
trialkoxysilanes/Harada, Masayoshi, Yamada, Yoshinori, 1994. [4]
U.K. Patent No. 2263113: Process for producing
trialkoxysilanes/Yamada, Yoshinori, Harada, Katsuyoshi, 1993. [5]
Japanese Patent Laid-Open Publication No. 05-178864: Preparation of
trialkoxysilanes/Yamada, Yoshinori, Harada, Masayoshi, 1993. [6]
U.S. Pat. No. 3,641,077: Method for preparing alkoxy derivatives of
silicon germanium tin thallium and arsenic/Rochov E. G. 1972. [7]
U.S. Pat. No. 2,380,997: Contact masses/Patnode Winton. 1945. [8]
U.S. Pat. No. 2,473,260: Preparation of tetramethyl silicate/Rochov
E. G. 1946. [9] U.S. Pat. No. 4,314,908: Preparation of reaction
mass for the production of methylchlorosilane/Downing James; Wells
James, 1982. [10] U.S. Pat. No. 4,727,173: Process for producing
trialkoxysilanes/Mendicino F. D. 1988. [11] U.S. Pat. No.
3,775,457: Method of manufacturing alkoxysilanes/Hisashi Muraoka,
Yokohama, Kanagawa-ken. 27.11.73 [12] U.S. Pat. No. 4,762,939:
Process for trialkoxysilane/tetraalkoxysilane mixtures from silicon
metal and alcohol. 1988. [13] U.S. Pat. No. 5,783,720:
Surfase-active additives in the direct synthesis of
trialkoxysilanes/Mendicino, Frank, Childress. 1998. [14] U.S. Pat.
No. 6,090,965: Removal of dissolvent silicates from alcohol-silicon
direct synthesis solvents/K. M. Lewis, Hua Yu. 2000. [15] U.S. Pat.
No. 5,166,384 (US) Method for the removal of siloxane dissolved in
the solvent employed in the preparation of trimethoxysilane via
methanol-silicon metal reaction/Donald L. Bailey, Thomas E.
Childress, Newport, both of Ohio. 1992. [16] U.S. Pat. No.
5,362,897: Process for producing trialkoxysilane/Katsuyoshi Harada,
Yashinori Yamada. 1994. [17] U.S. Pat. No. 4,931,578: Process for
the preparation of alkoxysilane/Yoshiro Ohta, Kamida-chou,
Izumi-ku. 1990. [18] Japanese Patent Laid-Open Publication No.
06-312994: Preparation of alkoxysilanes/Harada, Masayoshi, Yamada,
Yoshinori. 1994. [19] Japanese Patent Laid-Open Publication No.
06-312992: Preparation of alkoxysilanes/Harada, Masayoshi, Yamada
Yoshinori. 1994. [20] Japanese Patent No. (Sho)50-34540:
Alkoxysilanes/Masafumi Asano, Kawasaki, Taizo Ohashi 1975. [21]
Japanese Patent No. (Sho)51-1692: Process for producing
trialkoxysilanes/Hisashi Muraoka, Yokohama, Masafumi Asano, 1976.
[22] U.S. Pat. No. 5,177,234: Preparation of alkoxysilanes by
contacting a solution of hydrogen fluoride in an alcohol with
silicon/Binh T. Nguyen. 1993. [23] U.S. Pat. No. 4,487,949: Process
for preparation of alkyl silicates/Charles B. Mallon, Belle Mead,
N.J., 1984. [24] European Patent No. 517398: Preparation of
alkoxysilanes using HF (salt) and silicon and alcohol/Bank, Speier,
John Leopold, 1992. [25] WO 2007/032865: PROCESS FOR THE DIRECT
SYNTHESIS OF TRIALKOXYSILANE [26] Russian Federation Patent No.
2235726 C1: Method for preparing alkoxysilanes/Gorshkov A. S.,
Markacheva A. A., Storozhenko P. A., 2003
DISCLOSURE
Technical Problem
In order to solve the above problems, an object of the present
invention is to provide:
(i) removing or significant reducing induction period of synthesis
reaction
(ii) guaranteeing consistent removal of impurities contaminating
solvent and acting as a catalyst of a side reaction, and products
from a side reaction, from reaction environment; and
(iii) ensuring synthesis reaction of trialkoxysilane in continuous
mode.
Technical Solution
In one general aspect, a method for preparing trialkoxysilane
includes:
(a) pulverizing silicon (Si) into fine particles having a size of
30-100 .mu.m in a solvent environment, wherein the solvent is
directly used in a later synthesis process of alkoxysilane;
(b) continuously synthesizing trialkoxysilane by continuously
feeding a suspension of silicon and anhydrous alcohol in an amount
consumed in a reaction in a synthesis process of trialkoxysilane to
a reactor, wherein the amount of consumed suspension is calculated
from an amount of synthesized trialkoxysilane using following
Equation 1, so that an amount of silicon fed to a reactor as a
suspension component, and an amount of silicon after a reaction is
completed in a reaction process are maintained the same, thereby
feeding a suspension so that a reaction proceeds consistently and
stably, mSi=k1mTES+k2mTEOS [Equation 1]
wherein, mTES is mass of triethoxysilane, mTEOS is mass of
tetraethoxysilane obtained per unit time as a result of direct
reaction, and k1 and k2 are molar ratios of silicon consumed in
synthesis processes of triethoxysilane and tetraethoxysilane,
respectively; and
(c) removing impurities accumulated in a reactor in a manner of
continuously bleeding a solvent using a ceramic membrane filter
from a reactor, wherein a solvent is supplemented by continuously
feeding an amount of bled solvent as a suspension component to a
reactor.
In addition, the object of the present invention is established by
the following preferred embodiments:
The silicon may have a linear dimension of 20 mm to 20 cm prior to
pulverizing.
A required amount of a catalyst may be directly put into a silicon
mass in the pulverizing process in a solvent environment.
The catalyst may be used in an amount of 1.0-10.0 wt % relative to
silicon.
A mass ratio of the solvent and the silicon may be 1:2 to 2:1.
The solvent may be heated to 160 to 300.degree. C. in the synthesis
process of trialkoxysilane.
The suspension may be continuously mixed before fed to a reactor,
in order to maintain a stable ratio of the amounts of silicon,
solvent and catalyst.
The amounts of the silicon, the solvent and the catalyst in a
reaction environment may be constantly maintained throughout the
entire synthesis processes of trialkoxysilane.
The solvent containing impurities formed therein as the reaction
proceeds, may be bled through a ceramic membrane filter equipped in
a reactor.
The ceramic membrane may have a pore size of 1 to 10 .mu.m.
The solvent bled in a reaction environment may be used in the
process through a purification operation.
Advantageous Effects
As described above, according to the present invention, in the raw
material preparation, a silicon raw material is ground in a solvent
environment without contact with air, so as to take an action for
preventing the formation of oxide film on the surface of silicon;
and in the technical process, by guaranteeing reaction activation,
the initial induction period of the reaction of silicon and alcohol
is dramatically shortened, unlike the prior arts, and thus,
processing time is shortened, resulting in maximizing productivity,
and making the method economical.
Moreover, since the pulverizing process of silicon which is a
preparation operation of raw material is carried out in the
environment using the same solvent as used in the later synthesis
process, the technical process is not complicated but simplified,
and since the consumed suspension is continuously fed, continuous
process is possible.
Besides, wet process is used in pulverizing silicon, so that the
generation of silicon fine dust having a risk of explosion during
interaction with oxygen in the air is prevented, thereby securing
stability, and the solvent is bled through a ceramic membrane
filter to continuously remove impurities in reaction environment,
thereby maintaining reaction conversion rate of silicon raw
material consistently high without an additional process in
continuous mode, and thus, making the method economical.
Therefore, since in the process for preparing trialkoxysilane,
continuous synthesis process is possible through the reduction of
induction period of direct synthesis reaction, and continuous
removal of impurities, and thus, both dramatic shortening of entire
processing time, and continuous production of trialkoxysilane are
possible, the present invention may maximize productivity and
economic efficiency.
DESCRIPTION OF DRAWINGS
FIG. 1 is a graph representing yields of reaction products
(triethoxysilane; TES) over time in each Example according to the
present invention and Comparative Example.
BEST MODE
The present invention provides a method for preparing
trialkoxysilane including activation of reaction mass through
interaction of anhydrous alcohol and silicon ground in the
pulverizing process, in particular without contact with an
atmosphere in a solvent environment, removal of impurities, and
supplement of consumed amount of raw material, and trialkoxysilane
may be synthesized through the following sequential steps:
(a) Silicon is ground into fine particles having a size of 30-100
.mu.m in a liquid environment, preferably a solvent environment,
wherein the liquid (or solvent) is directly fed and used as a
solvent in a later synthesis process of trialkoxysilane. It is
important that pulverizing is carried out in a liquid environment,
more preferably, a solvent environment when considering reaction
solvent to be used later.
(b) silicon is continuously fed to a reactor in a suspension state
together with a solvent in an amount consumed in synthesis process
of trialkoxysilane, wherein an amount of silicon fed to a reactor
as a suspension component, and an amount of silicon after a
reaction is completed in a reaction process are maintained the
same, so that the progress of the reaction is maintained in
consistent and stable state. In this case, the amount of consumed
suspension and the amount fed as suspension are calculated from the
amount of synthesized trialkoxysilane, by the above Equation 1.
(c) Impurities accumulated in the reactor is removed in a manner of
continuously bleeding a solvent from the reactor using a ceramic
membrane filter, wherein the solvent is continuously fed to the
reactor as a suspension component in a bled amount, thereby
guaranteeing supplement.
In the present invention, trialkoxysilane represented by the
following Chemical Formula 1 may be preferably prepared.
SiH(OR).sub.3 [Chemical Formula 1]
wherein, R is methyl, ethyl, propyl or isopropyl group having 1 to
3 carbon atoms.
Physical basis of the technical measures suggested by the present
invention in the first step of reagent activation is the condition
where the silicon raw material is ground not in the air like the
prior art method, but in a solvent environment, thereby preventing
formation of natural oxide layer on the surface of silicon fine
particles produced after pulverizing. The oxide layer is
necessarily produced on the surface of all metal silicon when
contacted with oxygen in the air. Such oxidation reaction is
possible at all temperatures including room temperature,
independently of chemical purity of silicon, that is, it may occur
in any case where silicon is ground in the air as in prior art
methods.
Meanwhile, natural oxides as mentioned above existing on the
surface of ground silicon particles cause all the difficulties in
the technical process for interaction of silicon and alcohol, which
are generation of reaction `induction period`; the requirement of
heating a mixture of ground silicon in [1] and a catalyst;
production of unreacted silicon from incomplete reaction; use of
additional catalyst in the form of halides [1], or the requirement
of recovering concentrated mixture into a reaction mass [26]; and
consequently, very complicated technique and design of
equipment.
In the case of the method suggested by the present invention, the
main disadvantages of the prior art methods are excluded, since
silicon is ground in a liquid environment, that is, solvent
environment, so that there is no contact with atmosphere, and an
oxide layer is not formed on the surface of silicon particles
produced from pulverizing. That is, it has an active surface. There
is no contact with an air, and at the same time, oxidation does not
occur from the contact with a solvent. Later, the solvent is
continuously used in the chemical reaction of the main technical
process as its original use. In this way, the formation of oxide
layer on the surface of the initial silicon particles is prevented
by the technical measures according to the present invention, and
thus, the activation of main technical process reagent, being
prepared for immediate progress of synthesis reaction of
trialkoxysilane, is guaranteed.
Besides, the ground fine particle size of the present method is
30-100 .mu.m, which is up to 10 times smaller than [1] and [26], so
that the contact area of main reagents is greatly increased, and
consequently induction period is significantly shortened. In
contrast, as suggested in practicing process of [26], similarly to
[1], in case silicon is ground to such a small size in the air,
since natural oxide film is formed on the surface of silicon, in
the state of having significantly increased total surface area as
compared to unground silicon, which is caused by making the size of
fine particles small, induction period is increased, and other
disadvantageous characteristics are strengthened.
Another main disadvantage of [26] is that reaction mixture is
concentrated over many times by newly adding reagents to unreacted
silicon, and for this, deposits in the suspension should be
periodically bled, and long term precipitation is required. The
present invention solves this problem by carrying out such
operation in continuous manner. Herein, the present invention uses
bleeding process of a suspension through a ceramic membrane filter
in order to prevent coarse fine particles of silicon having
reactivity from being removed from the reactor. The amount of
silicon fed to the reactor as a suspension component is maintained
the same as the amount of reacted silicon, and the amount of
reacted silicon is determined by the amount(s) of synthesized
trialkoxysilane and/or hydrogen formed as a result of the reaction.
Solvent is continuously bled in the outlet of the reactor, and the
solvent is fed to the reactor in the bled amount as a suspension
component, to supplement bled amount, thereby removing impurities
in the reactor.
By selecting 20 mm or more, preferably 20 mm to 20 cm as a linear
dimension prior to pulverizing, the possibility that significant
amount of silicon fine particles, on the surface of which oxides
exist, are put into the reaction mixture, may be certainly
prevented.
The characteristics represented by adding a catalyst to silicon
mass prior to pulverizing of silicon are as follows: First, two
materials are ground into the same size. Second, the above
materials are homogeneously mixed within the suspension in the
solvent environment in which silicon was ground as characterized by
the present invention. The pore size in a ceramic membrane filter
is 1 to 10 .mu.m. If the pore size is smaller than 1 .mu.m,
filtering is difficult, and if larger than 10 .mu.m, silicon fine
particles having reactivity is removed through a filter, and loss
of silicon increases. If the initial size of silicon fine particles
is 30 to 100 .mu.m, adequate pore size in ceramic membrane filter
is 5 .mu.m, wherein total loss of silicon is less than 0.5%.
The method of the present invention may be realized as follows: For
example, initial silicon which is metal silicon having a purity of
98-99% is ground into a desired size using a hammer mill (particle
size .about.1 mm) and a general planetary ball mill, and working
capacity is previously filled with a solvent. The solvent functions
as thermal oil, and as such solvent, for example, alkylated
benzene, alkylated naphthalene, polyaromatic oil, and the like may
be used, preferably, as in [26] and other similar methods,
THERMINOL.RTM. 66 or other polyaromatic oil may be used. According
to the present invention, in the solvent environment, silicon
pulverizing process is carried out until the fine particle size is
reached to 30-100 .mu.m, and obtained suspension is continuously
fed to the reactor using dosing pump, so that the interaction of
silicon and alcohol continuously occurs, but silicon powders are
not separated from the solvent. In the reactor, planned capacity
and contact mass of the components are formed.
The suspension component added for consistently maintaining the
reaction in an amount consumed in the synthesis process includes
silicon, corresponding solvent and catalyst, and the amount of
silicon is calculated from the amount of synthesized
trialkoxysilane using Equation 1. The suspension is consistently
and stably fed into the reaction.
As anhydrous alcohol, anhydrous ethanol or anhydrous methanol which
are well known in the art, may be used. In addition, as a catalyst,
copper-containing catalyst such as CuCl may be used.
The main process is carried out at temperature ranging
180-260.degree. C. as in [26], under a environment of a solvent
having high boiling point such as THERMINOL.RTM. 59, THERMINOL.RTM.
60, THERMINOL.RTM. 66, DOWTHERM.RTM. HT, MARLOTHERM.RTM. S,
MARLOTHERM.RTM. or other polyaromatic oil, as mentioned above. That
is, the core of the main technical process is to fill reaction
capacity in any well-known form with a suspension (catalyst-added
silicon, for example, including ground silicon and CuCl powders in
an environment of a solvent such as THERMINOL.RTM. 66), then
strongly mix the mixture with heating to 180-260.degree. C., and
adding alcohol such as ethanol or methanol. Generated vapor-gas
mixture and liquid are continuously removed from reaction capacity,
and separated by any well-known technical method including those
used in [1], [26], or other similar methods. Triethoxysilane to be
desired or trimethoxysilane is also separated by such general
methods.
The present invention may continuously bleed a solvent using a
ceramic membrane filter, differently from the prior arts, and in
particular, induction time may be dramatically shortened through
the difference of pulverizing process of silicon raw material.
As mentioned above, in the prior arts, since silicon raw material
are ground in the air, and the oxide film is inevitably formed on
the surface of silicon, the existence of induction period which is
the most important factor in the synthesis of trialkoxysilane is
inevitable. Induction period is also necessarily undergone when in
later continuous process, suspension is bled to additionally feed
raw material. However, in the present invention, initial synthesis
induction period which is inevitable in the synthesis of
trialkoxysilane, may be removed or dramatically shortened, and
using a ceramic membrane, impurities may be continuously removed in
continuous process.
Meanwhile, according to the present invention, in case of carrying
out only process (a), and using conventional method as the rest of
synthesis processes, significant improvement is confirmed, and in
case of carrying out only processes (a) and (b), and not process
(c), also excellent effect is confirmed. Therefore, the cases where
process (b) or processes (b) and (c) are omitted are also
understood as improved inventions, respectively.
Hereinafter, the present invention will be described in detail by
the following Examples, but is not limited thereto.
The Examples of the present invention are based on the experimental
results in a specially designed equipment for synthesis of
trialkoxysilane.
Example 1
The preparation of triethoxysilane was carried out in a reactor
having working capacity of 9 L, which was equipped with an electric
heating control device of reaction capacity, and an impeller
stirrer having 4 wings to control rotational speed to 300-1500 rpm.
3.3 kg of metal silicon was ground in a solvent environment of 6.6
kg of THERMINOL.RTM. 66 using Planetary Mill until the particle
size is 30-100 .mu.m. In the pulverizing process, 0.2 kg of CuCl
catalyst was put into the suspension. In the state of continuous
operation of the stirrer at 850 rpm, contact mass was heated to
temperature of 242+2.degree. C., the feed of ethanol as anhydrous
alcohol to the reactor was started at 600 ml/hr using dosing pump
(Digital dosing pump), GRUNDFOS.RTM. DME 60-10 AR. Samples were
taken when liquid product was generated in the reactor, then every
30 minutes. As a result of analysis of the samples in Gas
chromathograph, Agilent.RTM. GC7890A, synthesis reaction was
started 10 minutes after alcohol was poured, and reaction rate
increased for initial 60 minutes. The synthesis reaction rate of
triethoxysilane decreased after 180 minutes, and completely slowed
down 260 minutes after alcohol was fed. Herein, 1635 g of
triethoxysilane and 105 g of tetraethoxysilane were obtained. The
selectivity of triethoxysilane was 94%.
Comparative Example
This experiment is carried out in the same condition as Example 1,
except for the preparation process of reaction reagent. Metal
silicon was ground in the air using Planetary Mill until the
particle size is 30-100 .mu.m. 3.3 kg of ground silicon, 6.6 kg of
THERMINOL.RTM. 66 as a solvent, and 0.2 kg of CuCl catalyst were
put into the reactor, and the reaction was started. As a result of
analysis of the samples, the reaction of metal silicon and ethyl
alcohol was started 150 minutes after alcohol was fed, then
reaction rate gradually increased. The synthesis reaction of
triethoxysilane was slowed down 500 minutes after alcohol was fed.
For 500 minutes, 1435 g of triethoxysilane, and 614 g of
tetraethoxysiane were obtained. The selectivity of triethoxysilane
was 70%.
Example 2
This experiment was carried out in the same condition as Example 1,
except that in the reaction with anhydrous ethanol, silicon was
continuously fed to the reactor, depending on the amount of
consumed solvent, in the state of mass ratio of solvent and silicon
in suspension components of 2:1. In the synthesis process of
trialkoxysilane, silicon of suspension component was fed to the
reactor, and as a result of reaction, it was fed in the same rate
as the consumption rate of silicon. The amount of consumed silicon
per time unit was calculated from reaction mass-balance according
to a formula such as above Equation 1. mSi=k1mTES+k2mTEOS
wherein, mTES is mass of triethoxysilane, mTEOS is mass of
tetraethoxysilane obtained per unit time as a result of a direct
reaction, and k1 and k2 are coefficients related to molar ratios of
silicon consumed in synthesis processes of triethoxysilane and
tetraethoxysilane, respectively. In the present Example, it was
confirmed that k1=0.171, and k2=0.135. As described above, silicon
as a suspension component was continuously put into the reactor in
the amount calculated from above Equation 1. At the same time,
solvent was continuously bled through a ceramic membrane filter
equipped in the reactor body. The solvent in which impurities
dissolved was collected in a collection container for recycling.
After filtering unreacted silicon and catalyst by forming vacuum to
10 mbar from the back of the ceramic membrane filter, the solvent
was discharged. Herein, the solvent was continuously discharged
through a ceramic membrane from the reactor, and its output was
double of mSi specified according to above Equation 1, which is
equal to the amount of solvent fed in the reactor as a suspension
component. With this, contact mass components, and the levels of
the above components in the reactor are maintained constant. The
sample in the reactor was bled every 3 hours, and contact mass
components were controlled. The level of contact mass in the
reactor was visually confirmed through a window of the reactor.
Synthesis reaction was started 10 minutes after alcohol was fed to
the reactor, and the reaction rate sharply increased for initial 60
minutes, then slowly increased for 120 minutes, and was stabilized
at triethoxysilane synthesis level of 420-450 g/h. For 500 minutes,
600 g of silicon and 1200 g of THERMINOL.RTM. 66 solvent were
continuously fed as suspension components. During this period, 3380
g of triethoxysilane and 141 g of tetraethoxysilane were obtained.
The selectivity of triethoxysilane was 96%.
Example 3
In this experiment, under the same condition as Example 2, the
amount of silicon consumed in the reaction of silicon and anhydrous
ethanol was calculated through Equation 1, and silicon was
continuously fed to the reactor in the state of mass ratio of
solvent and silicon in suspension components of 2:1. Difference was
that a ceramic membrane filter was not equipped, and the solvent
was not bled. Synthesis reaction was started 9 minutes after
alcohol was fed to the reactor, and the reaction rate increased for
first 90 minutes, then was stabilized at the level of
trietoxysilane of 400 g/h. Reaction was stopped 250 minutes after
feed of alcohol was started, by generation of large amount of foam
in the reaction product. During this period, 290 g of silicon and
580 g of THERMINOL.RTM. 66 catalyst were continuously fed to the
reactor as suspension components. Additional input of the solvent
caused the increase in the amount of contact mass in the reactor,
and generated foam in the reactor. For 250 minutes of reaction,
1600 g of triethoxysilane and 120 g of tetraethoxysilane were
obtained. The selectivity of triethoxysilane was 93%.
Following Table 1 shows the results of comparison of Examples and
Comparative Example.
TABLE-US-00001 TABLE 1 Time taken to start Reaction after
Pulverizing feeding method ethanol Fed amount Results of (induction
MG Bled amount TES TEOS silicon period, Si Solvent Solvent
productivity productivity TES Example powder minute) (g) (g) (g)
(g) (g) selectivity Example 1 Solvent 10 -- -- -- 1635 105 93
environment Comparative In the 150 -- -- -- 1435 614 70 Example air
Example 2 Solvent 10 600 1200 1200 3380 141 96 environment Example
3 Solvent 9 290 580 -- 1600 120 94 environment
As described above, the biggest difference of the technical
measures suggested by the present invention from the prior art
methods is, that in the raw material preparation, a silicon raw
material is ground in a liquid environment, so as to take an action
for preventing the formation of oxide film on the surface of
silicon; and in the technical process, by guaranteeing reaction
activation (Examples 1, 2 and 3), the initial induction period of
the reaction of silicon and alcohol is dramatically shortened,
unlike the prior arts, and thus, processing time is shortened,
resulting in maximization of productivity, and making the present
invention economical.
In addition, in case of feeding suspension (Examples 2 and 3), good
effects as compared to Comparative Example, such as TES
productivity, TES selectivity, dramatic shortening of initial
induction period, and the like were confirmed. In case of also
bleeding solvent (Example 2), very good effect of at least double
the TES productivity of Comparative Example for the same reaction
time was shown.
The technical solution suggested by the present invention is simply
realized using prior art equipments, and since above mentioned
preparation of raw material (pulverizing silicon) is carried out in
a solvent environment, that is, in an environment using a material
which is used as a solvent in a later technical process, the
technical process is not complicated, but simplified.
In addition, since the pulverizing process of silicon which is a
preparation operation of raw material is carried out in the
environment using the same solvent as used in the later synthesis
process, the technical process is not complicated and simplified,
and since the consumed suspension is continuously fed, and
continuous synthesis process through consistent removal of
impurities using a ceramic membrane filter, is possible, entire
processing time is dramatically shortened, and at the same time,
trialkoxysilane is continuously prepared, thereby maximizing
productivity and economic efficiency.
Summarizing the above description, the technical measures of the
present invention have the following effects: Reduction of
induction period of direct synthesis reaction; Continuation of
synthesis reaction of trialkoxysilane; and Continuous removal of
impurities in reaction environment by bleeding solvent through a
ceramic membrane filter.
Therefore, all technical problems are solved by realizing the
method of the present invention.
* * * * *